In colder regions of the globe electrical devices are used to heat automobile engines and interiors to facilitate engine starting and user comfort. Energy costs and conservation efforts have led to the widespread use of parking lot controls. These controls are designed to reduce energy consumption while still satisfying engine starting and user comfort constraints. Numerous algorithms have been devised to limit this consumption, ranging from simple timers to the most current proportional temperature controls (the colder it gets the more power is delivered).
Current parking lot controls are centralized, whereby all the loads of a parking lot are switched together on or off by a central contactor. Many inherent restrictions and limitations are imposed by this form of centralized control. Central contactor controls carry substantial installation and maintenance costs, with typical installation pay back periods in the order of five years or more. The longevity of mechanical contactors depend heavily on regular maintenance adding to operational costs.
Many lots impose a limit on power use for each vehicle. But since no adequate means of enforcement exists, it is left open to abuse. Often enough users abuse the set limits to trip the main breaker for a lot, inconveniencing all patrons. In addition, individual parking stall breakers are tripped due to temporary short circuits, overloads, etc. Since no feedback as to the presence of power is provided for users or maintenance personnel, this stall maybe without power for several days.
It is one object of the present invention to provide an improved apparatus for controlling and monitoring electrical automobile heating loads for the purpose of energy conservation. Redistributing control of parking lot electrical loads to each parking stall has major advantages over centralized control schemes. Capital costs of implementation are drastically reduced to pay back periods in the order of one year. This is due in part to the elimination of the central high current contactors and their associated wiring. Other gains are realized through better demand management control, energy conservation algorithms and user service as well as lower maintenance costs.
By fitting each outlet box (which controls two stalls) of a parking lot with a reprogramable microcontroller greater flexibility is realized. This increases the diversity of possible energy conservation algorithms that can be implemented. Helping management staff to meet patron requirements, maximize energy conservation and meet ever increasing budgetary constraints. Further, conservation algorithms can be updated, customized, or changed as new techniques become available since the device is reprogramable. Apparatus for the measurement of temperature or wind-chill is also provided enabling the most current conservation algorithms to be implemented.
One novel feature included is the ability to detect each load as it is asserted or removed. This enables the device to delay delivery of power to a newly asserted load for sometime. Reasoning that the vehicle has just arrived, it is still warm and should be for sometime. The length of this delay could be a fixed amount of time or calculated based on current temperature, wind-chill, etc. This feature may also assist local utilities with peak power demand management. Peak demand periods occur between 8 and 9 a.m., when people arrive at work and again 5 to 6 p.m., when people return home. The burden of these automobile heating loads maybe averted during these times with this new technique.
By including apparatus for sensing current being delivered to each load another dimension in control is added. This enables the effective enforcement of power consumption limits for each vehicle, assisting in local demand power management. Maintenance costs are reduced and user service is increased by the detection of overloads or short circuits. Enabling these loads to be switched "off" before the associated breaker can trip. Added safety is provided by helping to prevent faulty loads from starting fires or damaging property. This apparatus enables the use of economical solid-state contactors for delivering power to attached loads, reducing maintenance costs and boosting reliability.
Feedback to patrons is provided by visual or auditory apparatus. In the case of visual feedback two light emitting diodes (LED's) are provided, one green the other red for each stall. As an example, when a user asserts a load the presence of power is identified by a quick flash of the green LED (load within acceptable limits) or the red LED is lit solidly (overload is rejected). For auditory feedback different tones identify load acceptance or rejection and the presence of power.
A bi-directional infrared data communication interface is included increasing utility. From time to time general maintenance of parking lots are performed requiring power tools. To facilitate this whole parking lots are disabled with centralized controls. While with the present invention only required individual outlets need be disabled. With this data link operational modes and limits can be easily set and changed. Since this link is bi-directional the device can be used to collect operational data to be down loaded periodically at request. Providing management and maintenance with such diverse information as frequency of use, number of overloads and short circuits seen, amount of power delivered, temperature trends, etc. This information may then be used to help design better energy conservation algorithms and maintenance schedules.
An interface is provided to allow the microcontrollers program or firmware to be changed, making it field programmable. This increases the useful life and reduces manufacture costs. Useful life is increased by the fact the energy conservation algorithms can be kept up to date and customized to a particular application. Manufacturing costs are reduced by having to produce only one generic model. And by reprogramming the devices with self test and calibration routines, manufacture costs are further reduced.
One embodiment of the invention will now be described in conjunction with the accompanying drawings in which: